Versatile particles from water-soluble chitosan and sodium alginate for loading toxic or bioactive substance

Versatile hydrogel particles were obtained by cross-linking of water-soluble chitosan (WSC) with sodium alginate (SA) in an acid-free medium. The structure of the particles was investigated with Fourier transform infrared spectra, differential scanning calorimetry and thermogravimetric analysis. These characterization results confirmed that the product was physically cross-linked hydrogel consisted of WSC and SA. It was found that the swelling ratio of the particles depended on the formation time, which indicated that their cross-linking degrees were easily modulated. The particles showed high capability to bind heavy metal ions, acidic gas and basic gas. The adsorption capacities of the particles could reach 88.2 and 66.0 mg/g for Cu(2+) and Pb(2+), 33.8 and 30.3 mg/g for NH3 and H2S, respectively. Especially, the existence of water significantly enhanced the adsorption capacities for NH3 and H2S. In addition, the mild formation condition made the particles suitable for encapsulating bioactive substance. The loading efficiency of the beads for hemoglobin (HB) reached close to 100%. Moreover, the release behavior of the HB-loaded particles was pH-sensitive. In contrast, HB was deactivated during encapsulating it with chitosan and sodium alginate. Obviously, such a kind of particles was an attractive adsorbent or carrier.